Plant for the production of cement clinker using the oxy-fuel process, method for operating a plant for the production of cement clinker and using recirculated gas from a plant for the production of cement clinker

Description

[0001] The invention relates to a plant for the production of cement clinker using the oxy-fuel process, comprising a conveying device for transporting bulk material, wherein the conveying device has a connection to the cement clinker production plant, through which the bulk material to be transported enters the cement clinker production plant, characterized in that the conveying device further comprises a gas supply for supplying recirculating gas to the cement clinker production plant. The invention further relates to a method for operating a cement clinker production plant and the use of recirculating gas from a cement clinker production plant.

[0002] To produce cement clinker, calcareous rock is first ground together with silicate-containing rock into raw meal and then subjected to heat treatment in a cement clinker production plant within a nitrogen-rich combustion atmosphere in a nitrogen-rich reactor. During the heat treatment, carbon dioxide (CO₂) is formally driven off from the carbonate (CO₃²⁻) contained in the limestone. This heat treatment generates carbon dioxide (CO₂) from two sources: the combustion of fuels, whether renewable or fossil, and the driving off of carbon dioxide (CO₂) from the limestone (CaCO₃). To reduce carbon dioxide emissions into the atmosphere, some plants are now being operated without nitrogen or at least with low nitrogen levels, using carbon dioxide (CO₂) as the carrier gas. This alters the solid-state chemistry and the heat balance of the plant.The aim of producing cement clinker in a nitrogen-free or low-nitrogen, but carbon dioxide-rich, manner is to inject the carbon dioxide (CO₂) into underground caverns. The low nitrogen content of the carbon dioxide-rich exhaust gas to be injected significantly reduces the amount of compression required.

[0003] To provide exhaust gas from a cement clinker production plant with the highest possible carbon dioxide (CO₂) content, the plant can be operated using an oxyfuel process. In this process, the carbon dioxide-enriched exhaust gas is largely recirculated and enriched with oxygen (O₂) necessary for combustion. The objective is to produce a gas mixture consisting almost exclusively of carbon dioxide (CO₂) and water vapor (H₂O), and in particular to minimize nitrogen (N₂), which is considered a contaminant. Therefore, the ingress of atmospheric air from the surroundings into the plant, which operates under negative pressure, is detrimental. The typical proportion of false air in the exhaust gas of a clinker kiln line downstream of the heat exchanger ranges from 15% in a properly installed new plant to up to 30% in an older plant.A significant proportion of atmospheric air enters the oven system via the flour feed, since, firstly, the transport and metering devices used there can only be incompletely sealed against the ambient atmospheric air, and secondly, even within the fine bulk material stream, there is a high proportion of pore volume that is filled with atmospheric air.

[0004] According to the teaching of US patent application US 2007 / 278333 A1, a process for the production of cement clinker is disclosed. In this process, a sulfate carrier, as part of the starting material, is first dried and dehydrated separately from the rest of the starting material and then individually ground to a flour-like consistency in a roller mill. Transport from the drying and dehydration system is pneumatically operated. Atmospheric carrier gas from a roller mill is partially recycled back into the mill after dust removal.

[0005] Chinese patent application CN 109 312 984 A describes a calcinator as an entrained flow reactor containing various "treatment zones" where heat is produced. The entrained flow reactor includes a conduit that constitutes the reactor itself.

[0006] European patent application EP 2 922 800 A1 discloses the drying of moist waste in the exhaust air of a cooler in a cement clinker production plant. The moist waste is dried in a flash calciner-like entrained flow reactor using the exhaust air from the clinker cooler.

[0007] The invention is based on the objective of preventing the ingress of false air through the raw flour feed.

[0008] The problem according to the invention is solved by a system with the features of claim 1. Further advantageous embodiments are specified in the dependent claims to claim 1. Claims 4 and 5 claim a method for operating a system comprising such a conveying device and the use of recirculating gas for operating a pneumatic conveying device.

[0009] According to the invention, the conveying device has a further connection to the cement clinker production plant via a gas supply for recirculation gas. This gas supply displaces any atmospheric air during the transfer of the bulk material to be conveyed into the cement clinker production plant.

[0010] To control the quantity of the conveyed bulk material, the conveying device may be provided with a control device that adjusts the amount of gas supplied depending on the flow rate of the pneumatically conveyed bulk material, whereby the gas supply increases with a lower flow rate of the pneumatically conveyed bulk material and decreases with a higher speed of the pneumatically conveyed bulk material.

[0011] The invention is explained in more detail with reference to the following figures.

[0012] It shows: Fig. 1 shows a first embodiment of the conveying device according to the invention,

[0013] In Figure 1Figure 100 shows a sketch of one embodiment of the conveying device. This embodiment of the conveying device 100 is a pneumatic lifting device that transports bulk material 10 vertically, or at least with a vertical component, upwards using a gas flow of recirculated gas. Instead of atmospheric air, recirculated gas is supplied to the lower section of the pneumatic lifting device, which connects to the cement clinker production plant 20 via connection 110. A control device 130 can detect the flow velocity in the pneumatic lifting device using a sensor 131 and regulate the gas supply accordingly. The flow velocity decreases as the bulk material being conveyed is fed into the device.If the flow velocity in the pneumatic lifting device decreases, more gas must be supplied to maintain the flow velocity. Conversely, if the flow velocity increases, this indicates that less bulk material is being lifted. To reduce the flow velocity again, less gas can therefore be supplied to the pneumatic lifting device. REFERENCE MARK LIST

[0014] 10 bulk material 130 Control device 20 Attachment 131 sensor 100 Conveyor 110 Connection

Claims

1. Plant (20) for the production of cement clinker in the oxy-fuel process, comprising - a conveying device (100) for conveying bulk material (10), wherein the conveying device (100) has a connection (110) to the plant (20) for the production of cement clinker, in which connection bulk material (10) to be transported is transferred to the plant (20) for the production of cement clinker, wherein the conveying device (100) has a further connection to the plant (20) for the production of cement clinker, a gas supply for application with recirculation gas.

2. Plant according to Claim 1, characterized in that the conveying device (100) is a pneumatic lifting device.

3. Plant according to either of Claims 1 to 2, characterized in that the conveying device (100) has a closed-loop control device (130) which, depending on the flow velocity of the pneumatically conveyed bulk material (10), sets the amount of the gas supply, wherein the gas supply increases with a lower flow speed of the pneumatically conveyed bulk material (10) and decreases with a higher speed of the pneumatically conveyed bulk material (10).

4. Method for operating a plant (20) for the production of cement clinker, wherein the plant (20) for the production of cement clinker operates in the oxy-fuel process, and wherein the plant (20) for the production of cement clinker has at least one pneumatic conveying device (100) for bulk material, wherein recirculation gas is applied to the pneumatic conveying device (100).

5. Use of recirculation gas from a plant (20) for the production of cement clinker, wherein the system (20) for the production operates in the oxy-fuel process, for the operation of a pneumatic conveying device (100).